Screen Orientation API: screen.orientation & orientationchange event

Source/modules/screen_orientation/ScreenOrientationDispatcher.cpp

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "modules/screen_orientation/ScreenOrientationDispatcher.h"
+
+#include "modules/screen_orientation/ScreenOrientationController.h"
+#include "public/platform/Platform.h"
+#include "wtf/TemporaryChange.h"
+
+namespace WebCore {
+
+ScreenOrientationDispatcher& ScreenOrientationDispatcher::instance()
+{
+    DEFINE_STATIC_LOCAL(ScreenOrientationDispatcher, screenOrientationDispatcher, ());
+    return screenOrientationDispatcher;
+}
+
+ScreenOrientationDispatcher::ScreenOrientationDispatcher()
+    : m_needsPurge(false)
+    , m_isDispatching(false)
+{
+}
+
+void ScreenOrientationDispatcher::addController(ScreenOrientationController* controller)
+{
+    bool wasEmpty = m_controllers.isEmpty();
+    if (!m_controllers.contains(controller))
+        m_controllers.append(controller);
+    if (wasEmpty)
+        startListening();
+}
+
+void ScreenOrientationDispatcher::removeController(ScreenOrientationController* controller)
+{
+    // Do not actually remove the controllers from the vector, instead zero them out.
+    // The zeros are removed in these two cases:
+    // 1. either immediately if we are not dispatching any events,
+    // 2. or after didChangeScreenOrientation has dispatched all events.
+    // This is to correctly handle the re-entrancy case when a controller is destroyed
+    // while in the didChangeScreenOrientation() method.
+    size_t index = m_controllers.find(controller);
+    if (index == kNotFound)
+        return;
+
+    m_controllers[index] = 0;
+    m_needsPurge = true;
+
+    if (!m_isDispatching)
+        purgeControllers();
+}
+
+void ScreenOrientationDispatcher::purgeControllers()
+{
+    ASSERT(m_needsPurge);
+
+    size_t i = 0;
+    while (i < m_controllers.size()) {
+        if (!m_controllers[i]) {
+            m_controllers[i] = m_controllers.last();
+            m_controllers.removeLast();
+        } else {
+            ++i;
+        }
+    }
+
+    m_needsPurge = false;
+
+    if (m_controllers.isEmpty())
+        stopListening();
+}
+
+void ScreenOrientationDispatcher::didChangeScreenOrientation(blink::WebScreenOrientation orientation)
+{
+    {
+        TemporaryChange<bool> changeIsDispatching(m_isDispatching, true);
+        // Don't fire controllers removed or added during event dispatch.
+        size_t size = m_controllers.size();
+        for (size_t i = 0; i < size; ++i) {
+            if (m_controllers[i])
+                static_cast<ScreenOrientationController*>(m_controllers[i])->didChangeScreenOrientation(orientation);
+        }
+    }
+
+    if (m_needsPurge)
+        purgeControllers();
+}
+
+void ScreenOrientationDispatcher::startListening()
+{
+    blink::Platform::current()->setScreenOrientationListener(this);
+}
+
+void ScreenOrientationDispatcher::stopListening()
+{
+    blink::Platform::current()->setScreenOrientationListener(0);
+}
+
+} // namespace WebCore